Bacteriostatic finish for cellulosic fabrics

ABSTRACT

A FINE AQUEOUS DISPERSION OF A PHENOILIC BACTERIOSTATIC AGENT SUCH AS HEXACHLOROPHENE, WITH THE ADDITION OF ZIRCONIUM ACETATE AND A CELLULOSE CROSS-LINKING AGENT, IS CURED ONTO A CELLULOSIC FABRIC. THE RESULTING BACTERIOSTATIC FINISH IS DURABLE THROUGH TWICE AS MANY LAUDERINGS AS A FINISH OMITTING THE CROSS-LINKING AGENT.

United States Patent 3,594,113 BACTERIOSTATIC FINISH FOR CELLULOSICFABRICS Leonard Lifland, Wellesley Hills, Mass., and Leonard A. Stanley,Charlotte, N.C., assignors to The Kendall Company, Walpole, Mass.

No Drawing. Continuation-impart of application Ser. No. 774,509, Nov. 8,1968, which is a continuation-impart of application Ser. No. 632,927,Apr. 24, 1967, which in turn is a continuation-in-part of applicationSer. No. 457,437, May 20, 1965. This application Dec. 3, 1969, Ser. No.881,843

Int. Cl. D06m 13/34, 13/02 US. Cl. 8115.6 Claims ABSTRACT OF THEDISCLOSURE A fine aqueous dispersion of a phenolic bacteriostatic agentsuch as hexachlorophene, with the addition of zirconium acetate and acellulose cross-linking agent, is cured onto a cellulosic fabric. Theresulting bacteriostatic finish is durable through twice as manylaunderings as a finish omitting the cross-linking agent.

This application is a continuation-in-part of our c0- pendingapplication Ser. No. 774,509, filed Nov. 8, 1968, now abandoned, whichis a continuation-in-part of our abandoned application Ser. No. 632,927,filed Apr. 24, 1967, which in turn is a continuation-in-part of ourapplication Ser. No. 457,437, filed May 20, 1965, also abandoned.

The invention relates to a process for developing a durable non-toxic,non-irritating bacteriostatic finish on cellulosic textile fabrics, andto the products thereof. More particularly it relates to abacteriostatic finish which is elfective even after repeated commercialor home launderings in suppressing the growth and proliferation of theskin bacteria which are responsible for the development of unpleasantodors in perspiration.

It is recognized that the skin of normal, healthy individuals has aresident bacterial flora estimated to run as high as 10,000 per squarecentimeter. This bacterial population resides chiefly on the surface ofthe skin, varies in number from place to place and is understood to beprincipally responsible for the development, by bacterial degradation,of unpleasant odors from perspiration, which as exuded by the normalbody is sterile and odorless. It has, therefore, long been a goal oftextile technologists to develop a safe and eifective bacteriostaticfinish for garments to be worn in intimate contact With the human body.

Although literally hundreds of products are known to exert abacteriostatic or even bactericidal action toward normal and pathogenicbacterial flora, the majority of them are unsuitable for use as atextile finish intended for use in contact with the body.

Many are irritants: others are so insoluble in Water as to be effectiveonly in organic solvent solution: others, on the contrary, are so watersoluble as to leach right out of the fabric and resist fixation thereto:still others, such as certain heavy metal salts, are definitely toxic tothe human system.

One compound which is very effective as a bacteriostatic agent, andwhich shows no incidence per se of skin irritation, is hexachloropheneor 2,2-dihydroxy-3,5,6,- 3',5',6-hexachlorodiphenyl methane. This whitecrystalline powder, although soluble in a variety of organic solvents,is insoluble in water. When applied to fabrics from, for example,acetone solution, hexachlorophene residues on a carefully dried fabricwill show bacteriostatic action. However, the hexachlorophene is merely3,594,113 Patented July 20, 1971 "Ice physically present on the fabric,without even a superficial fixation thereto: mechanical manipulation ofthe fabric, and especially the agitation connected with laundering andthe emulsifying, action of soaps or detergents, rapidly remove theinsoluble and unfixed material and leave the fabric unprotected. Thistype of transient effect will often not even survive the rigors oflaying-out, cutting, fabricating, packing, shipping and displayinggarments treated with organic solutions of hexachlorophene, and no validclaims of durable eifects therefrom can be substantiated.

It is with a method of more durably complexing phenolic bacteriostaticagents such as hexachlorophene to certain fabric substrates that thepresent invention is concerned. It has been found that an effective anddurable bacteriostatic finish can be developed on certain fabrics bycomplexing a small amount, generally not over 2% based on the fabricweight, of hexachlonophene to the fabric by means of a zirconiumcompound such as zirconium acetate or ammonium zirconyl carbonate, together with a finish of the cross-linking Wash-wear type. Surprisingly,the bacteriostatic efliciency of the phenolic compound is not masked ordiminished by the crosslinking finish, but instead is renderedunexpectedly more durable. As little as 2% of a cross-linking reactantfinish has been found to substantially double the number of launderingswhich a hexachlorophene treated fabric will survive and still showbacteriostatic activity.

It is therefore, an object of this invention to produce abacteriostatic, wash-resistant finish on cellulosic textile fabricswherein the bacteriostatic elfeot resides in a small amount of aphenolic bacteriostatic agent durably bonded to the fabric by means of azirconium complex and a cross-linking agent for the cellulose.

Other objects of the invention will be more fully understood from thefollowing description thereof.

Advantage is taken in this invention of the fact that certain salts ofmetals belonging to the fourth transition group of the Periodic Table,as typified by ammonium zirconyl carbonate and by the readily availablezirconium acetate Zr(OAc) (OH) can form coordination complexes withhydroxy compounds such as phenols. The discussion and example in thefollowing description of the invention will be illustrated by the use ofzirconium acetate, a preferred complexing agent due to its stable natureand its ready availability commercially. Certain phenolic compounds havebeen reported to be complexed to cellulosic fabrics, by means ofzirconium salts, to impart rot resistance to the fabrics (Gonzales etal, Textile Research Journal, vol. 33, No. 8, August 1963, pp. 600-608). The rot resistance developed, however, was sensitive to alkalineconditions, such as are met with in laun dering, and the phenolicfraction of the complex, which was responsible for the activity, wasreported to be removed. Hexachlorophene was not reported as one of thecompounds tried. It has been our experience that by complexing a smallpercentage of a phenolic bacteriostatic agent such as hexachlorophenetocellulosic fabrics by means of zirconium salts and a wash-wearcross-linking agent, a bacteriostatic finish is developed which understandard test conditions remains effective after repeated exposure toalkaline conditions as typified by home or commercial launderingoperations. In the case of hexachlorophine, the finish thus obtained isnot harmed by bleaching or scouring, and provides a high level ofbacteriostatic activity against a wide variety of Gram-positiveorganisms, and an apparently lower but still appreciable activityagainst Gram-negative organisms. In general, superior and more durableresults are obtained by using bisphenols than with mono-functionalphenolic compounds.

By cross-linking agents is meant here those reactants, whetherresin-forming or not, which are used to produce a wash-wear effect oncellulosic fabrics when used at the level of to Included in thiscategory are ureaformaldehyde, melamine formaldehyde, triazenes, triazones, dimethylol ethylene urea, dihydroxy dimethylol ethylene urea,and the carbamate resins.

The durability of phenolic bacteriostatic agents complexed to acellulosic fabric substrate by the process of this invention isdetermined in two ways: by the zone of inhibition shown by the fabricwhen grown on an agar plate containing common organisms such asescherichia coli and staphylococcus aureus, and by extraction. In thelatter procedure, a sample of the fabric is extracted with 0.1 N KOH,which removes the bacteriostatic agent quantitatively. The UV absorbenceof the aqueous extract is determined at 320 millimicrons, wherehexachlorophene has a sharp peak. The magnitude of the peak is aquantitative measure of the amount of hexachlorophene present, whencompared with standards of known strength. From this the percentage ofhexachlorophene on the fabric can be calculated.

On a theoretical basis, one mole of zirconium acetate should be capableof complexing one mole of hexachlorophene to a fabric, through one ofthe hydroxy groups of the biphenolic hexachlorophene. By the samereasoning, one mole of zirconium acetate should be capable of complexingtwo moles of a monophenolic bacteriostatic agent to a fabric substratecontaining groups with which the zirconium acetate will react.

It has been found that especially desirable and durable results areobtained if a theoretical excessi.e., two moles of zirconium acetate-isemployed for each mole of hexachlorophene. The exact nature of thiseffect is not understood.

Even better results are obtained if the mole ratio of zirconium acetateto each phenolic group in the bacteriostatic agent is increased to 1.5to 1: that is, 3 moles of zirconium acetate per mole of (bifunctional)hexachlorophene. Our effective limits are from two to ten moles ofzirconium acetate per mole of hexachlorophene, With a preferred ratio offrom three to six moles of zirconium acetate per mole ofhexachlorophene.

We have also found that a pleasant, fresh and appealing odor, persistentafter several launderings, may be imparted to cellulosic fabricsfinished by the process of this invention by incorporating small traces,of the order of 0.01% or less, of odorous phenolic compounds such asTexodor 2 BIs and Resodor 21, products of Sindar Corporation.

Complex phenolic bodies with a pleasant odor have been developed for thereodorization of finished textiles, and are used to mask chemical odorsand other offodors developed in storage of fabrics. As generally used,their influence is transient. By complexing such odorous phenolic bodiesto a fabric substrate by means of zirconium acetate, however, theirdurability of odor persists through five or more washing cycles,prolonging the consumer appeal of fabrics thus treated.

As stated above, pronounced durability of bacteriostatic efficiency isshown when the zirconium acetate-hexachlorophene complexing is carriedout in the presence of a wash-wear cross-linking finish applied to acellulosic fabric. Particularly effective are the carbamate resins,represented by dimethylol methyl carbamate and dimethylol ethylcarbamate, which have been postulated to react with cellulose asfollows, using the ethyl derivative as example:

C H OCON CH OH) Cellulose OH There is also the possibility that acertain amount of monomethylol ethyl carbamate, present in thedimethylol resin, will react with cellulose to give C H OCONHCH OCellu.

Alternatively, the dimethylol derivative may react with a singlecellulose molecule to give C H OCON(CH OH) (CH OCellu), which hydrolyzesin laundering to give C H OCONH CH O Cellu) Whatever the route by whichsuch a compound is formed, the amide hydrogen of this latter compoundmay be readily replaced by chlorine to form a chloramide of unusualstability, inasmuch as the chlorine does not degrade nor scorch thefabric during ironing, unlike the behavior of other nitrogen-containingwash-and-wear resins finished which form chloramides with availablechlorine.

The invention will be illustrated by the following examples.

EXAMPLE 1 A cotton broadcloth was treated with the following dispersion:

3% Triton X- (Rohm and Haas brand of ethylene oxide nonyl phenol) heatedabove F.

0.5% hexachlorophene 4% Alkanol HCS (Du Pont brand of nonionic ethoxyalcohol) 1.5% zirconium acetate 10% dimethylol ethyl carbamate 3.5%magnesium chloride 4.0% of a 35% dispersion of a polyethylene softener73.5% water In order to insure thorough dispersion, the hexachloropheneis dissolved in the wetting agents, and the water is then added, leavingthe hexachlorophene in the form of a very fine, almost colloidal,dispersion. To promote maximum bath stability, the zirconium acetate isadded just prior to processing the fabric.

The fabric was saturated with the above solution to 100% wet pickup in aconventional padder, dried at 225 R, cured for 5 minutes at 315 F.,after washed and redried.

Samples of the fabric thus treated and the same fabric after 10 homelaunderings and after 10 commercial launderings were tested with acontrol sample of untreated base fabric against Staphylococcus aureusaccording to the AATCC test #100l96lT. Circular disks 1% inches indiameter were cut from each of the 4 samples, placed in cups andsaturated with a culture of Staphylococcus aureus. After 24 hoursincubation at 37 C., 100 milliliters of letheen broth was added to thetest cups and an equal amount of sterile water to the test cups. Thecups were shaken vigorously for one minute and aliquots of serialdilutions were plated in petri dishes, which were incubated at 37 C. for24 hours and counted. The number of viable organisms on the samplestreated according to this invention ranged from 75 to 367: on theparallel control samples of base fabric they ranged from 318,000 to370,000. On a percentage basis, with three tests run on each of thethree treated fabrics, the degree of control as compared with the basefabric was 99.98% for the unwashed treated fabric, 99.86% from thehome-laundered treated fabric, and 99.76% from thecommercially-laundered treated fabric.

Even after 50 commercial laundering cycles, which is beyond the lifeexpectancy of wash-and-wear garments, fabrics treated as above with acombined carbamate resin finish and a cellulose-zirconiumacetate-hexachlorophene complexing finish showed inhibitory actionagainst Staphylococcus aureus and selected strains of Escherichia coli.Essentially identical results are obtained when any of theabove-mentioned cross-linking agents for cellulose are substituted forthe carbamate. By contrast, a parallel experi: ment omitting thecarbamate cross-linking agent yielded a fabric which showed little or nobacteriostatic action after 25 launderings.

One reason. for rewashing after the curing operation set forth above isto remove traces of the nonionic wetting agents used in the bathformulation to assist in solubilizing the hexachlorophene. It isadvisable to remove such nonionic stabilizers in a post-cure washingoperation, since their presence on the fabric seems to inhibit orinterfere with the bacteriostatic efficiency of the hexachlorophene.Alternatively, instead of a nonionic stabilizer, we have found thatphenolic compounds effective against organisms, such as hexachloropheneand ortho phenyl phenol, can be dissolved in warm 50% solutions ofcationic dispersing agents as represented by quaternary ammoniumcompounds such as alkyl dimethyl benzyl ammonium chloride, alkylethyl-benzyl dimethyl ammonium chloride, cetyl dimethyl benzyl ammoniumchloride, and the like, to form stable baths which quite unexpectedlyare infinitely dilutable and compatible with zirconium acetatesolutions. By use of such quaternary compounds, not only is thedeleterious effect of nonionic stabilizing agents avoided, but thequaternary ammonium compounds are themselves substantive on celluloseand display a bacteriostatic action of their own which broadens thespectrum of effectiveness of a treated cellulosic fabric.

The of carbamate resin used in the above example will impart a Wash-wearfinish to the fabric. However, as little as 1% resin will result inenhanced durability of the bacteriostatic finish (up to 50 launderingsor more). The fabric hand, at such low resin levels, is scarcelyaflected, with no crease-resistance or wash-wear effect noticeable. Ourpreferred limits of cross-linking agent are from 1% to on the weight ofthe fabric, depending on whether a wash-wear finish is desired or not.

Although hexachlorophene is our reagent of choice in thebacteriostat-resin finish combination of this invention, other phenolicbacteriostatic agents may be used, such as ortho phenyl phenol,halogenated phenolics such as tribromophenol, bithionol, and the like,the chief requirement being that the bacteriostatic agents contains atleast one phenolic hydroxyl group capable of complexing with cellulosethrough the intermediary of the bifunctional zirconium acetate, and thatin the concentration used, the phenolic compound should be nonirritatingand non-toxic when in contact with the human skin.

An additional phenolic bacteriostatic agent, with a broader activityspectrum than hexachlorophene, is 5-chloro-2-(2,4-dichlorophenoxy)phenol, produced by the Geigy Company and known as Irgasan CH-3565. Itmay be used alone, or in combination with hexachlorophene, asillustrated in the following example.

EXAMPLE 2 A cotton broadcloth was treated with the following dispersion:

10% Iegal CO-850 (General Anilines trademark for a nonyl phenoxypolyoxyethylene ethanol wetting agent).

0.5% hexachlorophene 5% zirconium acetate 5% Protorez AA (ProctorChemicals trademark for a 50% solution of a dimethylene propyleneurearesin) 0.9% of a 40% zinc chloride solution 78.1% water The fabric waspadded with the above to 70% wet pickup, dried at 250 F., cured for 90seconds at 340 F.,

afterwashed and redried. Even after 40 commercial launderings, thefabric showed antibacterial activity against Staphylococcus aureusaccording to the AATCC #-1965 Agar Plate Streak Test. Essentiallyidentical results were obtained when the CH3S65 hexachlorophenecombination was replaced by tribromophenol.

In general, we prefer to fix onto the fabric an amount of phenolicbacteriostatic agent not in excess of about 2% on the Weight of the dryfabric, to avoid discoloration and boardiness associated with excessivefabric loading with reagents of this type. The amount of zirconiumacetate employed will vary with the molecular weight of particularphenolic compound chosen, and is, therefore, best expressed on a molebasis. In case an additional, odor-bearing phenolic compound is alsocomplexed to the cellulose, the amount of zirconium acetate employed maybe increased slightly. The extra amount of zirconium acetate needed canbe calculated from the molecular weight of the odor-bearing phenoliccompound, but in general will not exceed about 0.2%.

Having thus described our invention, we claim:

1. The process for producing a durable laundry-resistant bacteriostaticfinish on a cellulosic fabric which comprises preparing an aqueousdispersion comprising a phenolic bacteriostatic agent, a wetting agentselected from the class consisting of non-ionic and cationic wettingagents, zirconium acetate, about 1% to 15%, based on the dry weight ofthe fabric of an aminoplast; cross-linking agent for the cellulose and acatalyst for promoting cross-linking,

impregnating said fabric with said aqueous dispersion,

and drying, and curing the impregnated fabric.

2. The process according to claim 1 wherein the phenolic bacteriostaticagent is selected from the class consisting of hexachlorophene,tribromophenol, 5-chloro- 2-(2,4-dichlorophenoxy) phenol and mixturesthereof.

3. A product prepared by the process of claim 1 in which not more than2% of the phenolic bacteriostatic agent is complexed to the cellulose bybetween 1.5 and 3 mole equivalents of zirconium acetate for eachphenolic hydroxy group on the bacteriostatic agent, said percentagebeing based on the dry weight of the fabric.

4. A cellulose fabric prepared by the process of claim 1.

5. A cellulose fabric prepared by the process of claim 2.

References Cited UNITED STATES PATENTS 3,183,149 2,850,407 8/1958Zurawie et a1 117l39.4 2,774,746 12/1956 Shelly et al. 260---29.4

FOREIGN PATENTS 760,344 9/ 1954 Great Britain.

OTHER REFERENCES Gonzales et a1., Textile Research Journal, vol. 33, No.8, August 1963, pp. 600-608.

GEORGE F. LESMES, Primary Examiner B. BE'IIIS, Assistant Examiner U.S.Cl. X.R. 8-116, 116.2

5/1965 Gonzales 16738.7

